An 84-day randomized trial found that a prescribed high-fiber intervention produced lower HbA1c and BMI than metformin alone in adults with newly diagnosed type 2 diabetes and overweight or obesity. The provocative result is preliminary and does not show that people should replace prescribed metformin with fiber.
What changed
Forty-eight adults at one Chinese hospital were randomized 3:1 to a customized diet using two standardized fiber formulas without glucose-lowering medication, or metformin monotherapy; 46 completed the study. At day 84, baseline-adjusted HbA1c averaged 6.3% with fiber versus 6.7% with metformin, while BMI averaged 28.4 versus 30.2 kg/m². The fiber group also showed lower glucose variability and changes in microbial species and functions. The paper was published October 2, 2026, and reported October 7.
How strong is the evidence?
This is peer-reviewed human randomized evidence with metagenomic testing. However, it was open-label, single-center and short, with only 12 participants in the metformin group. Investigators were not blinded.
What remains uncertain
The fiber group ate fewer calories and less protein, fat and carbohydrate, so fiber or microbiome changes cannot be isolated as the cause. The intervention used adjustable formulas containing several fibers rather than a simple food recommendation. Larger independent trials must test durability, safety and clinical outcomes. The authors reported public funding and no commercial conflict.
Why it matters
The study supports food-and-microbiome research in early diabetes, but HbA1c and BMI are surrogate outcomes. Anyone taking metformin or other glucose-lowering medicine should not stop or change it without clinical supervision.
Sources
Original study in Frontiers in Microbiology · Research report
Illustrative stock photograph by Shashi Chaturvedula on Unsplash; it does not depict the study foods, participants or results.
